The effect of macronutrient composition of breakfast on satiety and cognitive function in undergraduate students
Purpose It is believed that breakfast is an important meal due to its effect on appetite control and cognitive performance, yet little evidence exists to support this hypothesis. Methods Using a crossover design, 33 healthy undergraduates (aged 22 ± 2 years with a BMI of 23.5 ± 1.7 kg/m2) were randomized one of four breakfast treatments: no breakfast, a low-protein breakfast containing no animal protein, a high-carbohydrate/low-protein breakfast containing animal protein or a low-carbohydrate/high-protein breakfast. After an overnight fast, participants reported to the laboratory and baseline appetite questionnaires and cognitive tests were completed. A baseline blood sample was also collected. These measures were repeated at regular intervals throughout the test session. An ad libitum lunch meal was provided 240 min after breakfast, and the amount eaten recorded. Diet diaries and hourly appetite questionnaires were completed for the rest of the day. Results The no-breakfast treatment had a marked effect on appetite before lunch (p < .05). Moreover, participants consumed more energy at lunch following the no-breakfast treatment (p < .05). There was no difference in appetite before lunch or food intake at lunch following any treatment when breakfast was eaten. However, food intake over the entire test day was lowest for the no-breakfast treatment (p < .05). Plasma glucose and insulin were lower following the high-protein/low-carbohydrate treatment compared to the low-protein/high-carbohydrate—no animal protein treatment (p < .05). Participants were less happy when they missed breakfast (p < .05), but there were no other statistically significant effects of breakfast on mood or cognitive performance. Conclusions These results suggest that changing the macronutrient content of breakfast influences the glycemic response, but has no effect on the appetitive or cognitive performance measures used in this present study.